1. Field of the Invention
The present invention relates to a novel azo dye compound, and a colorant-containing curable composition for color filter use which is preferable to form a color image of color filters used for liquid crystal displays and solid imaging devices (e.g., CCD and CMOS), and a color filter and a method of producing the color filter.
2. Description of the Related Art
It has been desired to develop a compound having high fastness in both light fastness and heat resistance in the fields of dyes and earnest studies have been made to develop such a compound. Particularly, in the fields of dyes soluble in a solvent or water, the development of compounds superior in both light fastness and heat resistance has been desired.
As dyes superior in both light fastness and heat resistance, for Synthesis Example, Cr complexes of phthalocyanine type compounds and azo type dyes are known. However, the phthalocyanine type dyes are unfit for absorption in the visible wavelength range from 400 to 500 nm and are therefore not useful as yellow or magenta dyes. Also, the phthalocyanine type compounds exhibit high light fastness due to their molecular associations and therefore have a problem concerning preserving stability: specifically, for example, dyes precipitate depending on the dissolution state of these phthalocyanine type compounds.
Also, it has been pointed out that the Cr complex of an azo type dye contains a Cr atom and is therefore harmful to humans and environments. It has been desired to improve the drawback of the Cr complex. On the other hand, the azo type dye is a useful dye which has a high chromatic value and can possess various absorption wavelengths. However, none of non-metallic complex types satisfying requirements for light fastness and heat resistance at the same time has been found yet.
As azo type dyes having relatively high light fastness among these azo type dyes, compounds (e.g., Acid Red 57) having a γacid as a coupling component and compounds (e.g., Acid Yellow 29) having pyrazolone as a coupling agent have been known for a long time. However, no compound also satisfying requirements for heat resistance at the same time has been found so far (see, for example, Patent References 1 to 4.
There is also the problem that the heat resistance and light fastness of these dyes are significantly reduced depending on working conditions. For example, one or both of the heat resistance and the light fastness are reduced depending on the type of fiber to be dyed or in the following cases: in the case where these dyes coexist with other dye compounds, a photoinitiator, a polymerizable compound and an oxidant/a reducing agent, in the case where these dyes are present under an environment permitting ozone to generate and in the case where these dyes are present under an environment permitting a singlet oxygen to generate.
Further, many dyes exhibiting high light fastness and heat resistance are decreased in solubility in water or a solvent, giving rise to a problem concerning industrial applicability.
In the meantime, a dying method, printing method, electrodeposition method and pigment dispersion method are known as a method of producing color filters used for liquid crystal displays and solid imaging devices.
The pigment dispersion method among these methods is a method of producing a color filter using a color radiation-sensitive composition prepared by dispersing a pigment in various light-sensitive compositions by a photolithographic method and has the merit that this composition is stable to light, heat and the like because it uses a pigment. Also, since a photolithographic method is used to carry out patterning, the positional accuracy of the patterning is high and therefore, this pigment dispersion method has been widely used as a preferable method to produce a color filter for a color display having a large image plane and high precision.
When a color filter is manufactured by the above pigment dispersion method, the radiation-sensitive composition is applied to a glass substrate by a spin coater or roll coater and dried to form a coating layer, which is then exposed pattern-wise to light and developed to form color pixels. This operation may be carried out every color to obtain a color filter.
As a specific example of the composition used in the above pigment dispersion method, negative type light-sensitive compositions using an alkali-soluble resin, a photopolymerizable monomer and a photoinitiator have been used (see, for example, Patent References 5 to 9).
In the meantime, it has been desired in recent years to develop a more precise color filter in applications such as solid imaging devices. However, in a conventional pigment dispersion system, it is difficult to more improve resolution and also, the conventional system has, for example, the problem that coarse particles of a pigment causes color unevenness. This is the reason why the pigment dispersion method is not suitable to applications, such as, solid imaging devices, for which fine patterns are required.
Instances using dyes soluble in solvents or water to solve the above problems have been known (see, for example, Patent Reference 10).
However, curable compositions containing a dye have new problems such as those described in the following (1) to (4). Specifically;
(1) it is difficult to obtain a liquid curable composition having a desired spectrum because dyes are usually less soluble in either an aqueous alkali solution or an organic solvent;
(2) it is difficult to control each solubility (developing characteristics) of a cured portion and uncured portion because many dyes interact with other components contained in a curable composition;
(3) a large amount of a dye must be added in the case where the molar extinction coefficient (ε) of the dye is low and it is therefore inevitable to decrease other components such as a polymerizable compound (monomer), a binder and a photoinitiator, giving rise to the problem that the curability of the composition, heat resistance after curing and the developing characteristics of a (non) cured portion are deteriorated; and
(4) dyes are usually inferior in light fastness and heat resistance to pigments.
In the case of an application to a color filter for solid imaging device unlike the case of an application to a semiconductor, the layer thickness of the curable composition must be 1.5 μm or less. It is therefore necessary to add a large amount of dyes in the curable composition, posing the same problem that is mentioned above.
The above problem makes it difficult to satisfy the practical requirements as to a fine and thin layer color pattern for a highly precise color filter.
For this, it has been desired to develop dyes and curable compositions which can solve the above problem.
Patent References:                [Patent Reference 1] P.L. Patent Invention No. 101484,        [Patent Reference 2] D.T. Patent No. 2714204,        [Patent Reference 3] FR No. 2303839,        [Patent Reference 4] Japanese Patent Application Laid-Open (JP-A) No. 58-152240).        [Patent Reference 5] Japanese Patent Application Laid-Open (JP-A) No. 2-199403        [Patent Reference 6] JP-A No. 4-76062        [Patent Reference 7] JP-A No. 5-273411        [Patent Reference 8] JP-A No. 6-184482        [Patent Reference 9] JP-A No. 7-140654        [Patent Reference 10] JP-A No. 2002-278056        